Along with the rapid distribution of information-related equipment and communication equipment such as personal computers, video cameras, and mobile telephones in recent years, the development of batteries that are utilized as electric power sources thereof has been considered important. Furthermore, the development of high output and high capacity batteries for electric vehicles or hybrid vehicles is in progress in the automobile industry as well. Currently, among various batteries, lithium batteries are attracting attention because of their high energy densities.
With regard to the lithium batteries that are currently available in the market, since liquid electrolytes including flammable organic solvents are used, installation of safety devices that suppress temperature increase at the time of short circuits, and structures for preventing short circuits are needed. Meanwhile, since lithium batteries that have been produced into all solid state batteries by converting the liquid electrolyte to a solid electrolyte layer do not use flammable organic solvents in the batteries, it is contemplated that simplification of safety devices can be promoted, and the lithium batteries are excellent in view of the production cost and productivity.
Among solid electrolyte materials, since a sulfide solid electrolyte material is so high in Li ion conductivity, various kinds of research thereof have been progressed. Also, as a sulfide solid electrolyte material, sulfide solid electrolyte materials containing an iodine element (I element) are known. For example, Patent literature 1 discloses a sulfide solid electrolyte material obtained by using Li2S, P2S5, LiI, and AS (AS is at least one kind of Al2S3, SiS2 and GeS2). Patent literature 1 also discloses usage of an oxide active material such as LiNi1/3CO1/3Mn1/3O2 as a cathode active material.